@article{AFM_1993_18_2_a7,
     author = {Lowell J. Hansen and Harold S. Shapiro},
     title = {Graphs and functional equations},
     journal = {Annales Fennici Mathematici},
     pages = {343--354},
     publisher = {mathdoc},
     volume = {18},
     number = {2},
     year = {1993},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/AFM_1993_18_2_a7/}
}